1. Field of the Invention
The present technology relates to the field of liquid carrying systems and the cleaning of the carrying systems, particularly commercial or residential drain, run-off systems or rain systems and pipes. These treatments include physical treatment of spurious coatings within the carriers and delivery of active ingredients and/or delayed activity ingredients.
2. Background of the Art
Biofilms are biological films that develop and persist at interfaces in aqueous environments, especially along the inner walls of conduit material in industrial facilities, in household plumbing systems, on medical implants, or as foci of chronic infections. These biological films are composed of microorganisms embedded in an organic gelatinous structure composed of one or more matrix polymers which are secreted by the resident microorganisms. Biofilms can develop into macroscopic structures several millimeters or centimeters in thickness and can cover large surface areas. These biological formations can play a role in restricting or entirely blocking flow in plumbing systems and often decrease the life of materials through corrosive action mediated by the embedded bacteria. Biofilms are also capable of trapping nutrients and particulates that can contribute to their enhanced development and stability.
The involvement of extracellular polymers in bacterial biofilms has been documented for both aquatic; and marine bacteria, and the association of exopolysaccharides with attached bacteria has been demonstrated using electron microscopy and light microscopy. The presence of such exopolysaccharides is believed to be involved in the development of the microbial biofilm. Analysis of biofilm bacteria isolated from freshwater and marine environments has shown that the polymers they produce are composed largely of acidic polysaccharides. The control and removal of biofilm material from pipe and conduit surfaces has historically been carried out by the addition of corrosive chemicals such as chlorine or strong alkali solutions or through mechanical means. Such treatments are generally harsh to both the plumbing systems and the environment, and have been necessary due to the recalcitrant nature of biofilms within those systems. The resistance to treatment by biocides has been due in large measure to the protective character of intact biofilm matrix polymers. Improperly or incompletely maintained water distribution systems containing metal, plastic, concrete or concrete/asbestos pipe may show scale formation, sedimentation and microbiological tubercular growth by iron, manganese, sulfate-reducing, organic acid-producing, aerobic and other bacteria. This scale, sedimentation and growth may result in restricted water flow, higher pumping costs, customer complaints of the water's appearance, odor or taste, low chlorine residues, health hazards, system leakage and poor performance of the distribution systems.
Mechanical cleaning methods such as pigging, scraping, reaming and honing have been used to remove blockages from water distribution systems. These methods, however, require extensive excavation and opening of the distribution system for insertion of the appropriate tools. Valves must usually be removed and replaced along with hydrants, while elbows and hydrant connects are not usually cleaned mechanically and thus remain uncleaned. Fire protection systems such as fire sprinkler systems are impossible to clean mechanically.
Underscale corrosion causes small pits in the walls of systems which cannot be completely cleaned by mechanical methods. The residues cause immediate “red water” problems when the system is put back into service due to rust. In addition, residual bacterial growth results in new tuberculation with resulting reduced flow. Because of these residues, mechanical cleaning is normally followed by cement lining, epoxy lining, or other insertion/lining process. However, lining only covers up these residues. In addition, it decreases the diameter of the pipe and adds substantially to the rehabilitation cost.
Many of these blocked distribution systems can be cleaned by a low cost process using chemical cleaning solutions that are circulated in isolated sections of the system. One such method is disclosed in U.S. Pat. No. 5,360,488 which is assigned to the assignee of the present invention and is hereby incorporated by reference in its entirety, along with assignee's U.S. Pat. No. 5,527,395 covering a chemical cleaning process improvement, and U.S. Pat. No. 5,680,877.
U.S. Pat. No. 7,094,394 (Davies et al.) discloses a method of cleaning or protecting surfaces by treatment with compositions comprising N-(3-oxododecanoyl)-L-homoserine lactone (OdDHL) blocking compounds and/or N-butyryl-L-homoserine lactone (BHL) analogs, either in combination or separately.
U.S. Pat. No. 6,076,536 (Ludwig et al.) describes a method to chemically clean and immediately passivate a water distribution system to quickly form a passivation layer. The system may be a potable water system, a non-potable water system, a water well or a fire protection system such as a fire sprinkler system and may be treated with a biocide. A section of the system is isolated and chemically cleaned, then is immediately passivated using a high concentration of passivating agent. A passivating layer quickly forms, then the concentrated passivating agent is removed and a maintenance concentration of passivating agent is added. The cleaned and passivated section is restored to the system to provide improved water flow.
U.S. Pat. No. 6,964,275 (Carl) describes methods and compositions for cleaning and maintaining chemical, biological and radiological countermeasure washdown systems are disclosed. Systems are effectively cleaned by the removal of water scale, including deposits, sediment, microbiological scale, microinvertebrate fouling, and the like, from the inside surfaces of piping in the system. A section of the system is isolated for cleaning and an aqueous acidic cleaning solution is circulated through the fouled pipe section to be cleaned for a sufficient time and at a controlled pH to dissolve and loosen the scale. After cleaning all of the sections, the system is restored to operational readiness.
Mechanical cleaning with “snakes” or augers is also difficult and can only be used on straight runs of pipe for removing only the loose debris in the center of the pipe. High pressure air, water jet and mechanical cleaning require almost complete dismantling of the system to create access for cleaning. Such dismantling requires extended periods of unacceptable downtime for the system and the ship.
Traditional means of chemical cleaning of scale from conventional (mostly iron) pipe systems by circulating acidic cleaning solutions through sections of the system to restore flow has been described in patents. U.S. Pat. Nos. 5,360,488 and 5,885,364 (Hieatt, et al.) describe a method for cleaning sections of potable water systems with acidic cleaning solutions. U.S. Pat. No. 5,527,395 (Ludwig, et al.) describes a chemical cleaning process improvement of U.S. Pat. No. 5,360,488. U.S. Pat. No. 5,680,877 (Edstrand, et. al) describes a system (equipment) for cleaning pipe sections of a water distribution network. U.S. Pat. No. 5,873,944 (Lien, et al.) describes a method of and a system for removing blockage from pipes in vacuum waste systems. U.S. Pat. No. 5,800,629 (Fyfe, et al.) describes a process for pipe system cleaning and in-line treatment of spent pipe system cleaning solution prior to disposal. U.S. Pat. No. 5,895,763 (Temple, et al.) describes a method for the controlled removal of carbonate scale from water conduit systems. U.S. Pat. No. 6,076,536 describes a method to chemically clean and immediately passivate a water distribution system. All of the above patents are assigned to the assignee of the present invention and are hereby incorporated by reference in their entirety. None of the above patents addresses the cleaning of countermeasure washdown systems, the scale associated with the countermeasure washdown systems or the cleaning of aluminum pipe associated with countermeasure washdown systems.
Additional patents describe physical/mechanical and chemical techniques to prevent the formation of various scales from forming in water pipe systems by treating the feed water. U.S. Pat. Nos. 4,328,638; 4,462,914; 4,561,983; 4,579,665; 4,816,163; 4,857,209; 5,192,451; 5,900,157 and 6,183,646 are examples. However, such physical/mechanical and chemical techniques are impractical for countermeasure washdown systems and none have been employed in combination with countermeasure washdown systems.
U.S. Pat. No. 6,183,646 (Williams) relates to the reduction and prevention of biofouling in facilities utilizing water, e.g. sea water, carrying biological organisms, without causing corrosion, chemical reaction or other detrimental action from the additive or environmental discharge problems. Such operations include, for example, desalination plants, power plants, oilfield water injection facilities and shipboard or ocean platform fire water systems. For example, in the desalination plant of FIG. 1, the biofouling reduction method and apparatus for this invention have a source of oxidizing agent such as chlorine ions or ozone, a source of copper ions and a dosing chamber for delivery of relatively low dosage levels of oxidizing agents and at appropriate times copper ions to form a treatment additive. Flow connectors connect the dosing chamber to various points along the piping in the desalination plant. A controller controls the operation of the dosing chamber and valves along the flow connectors to operate in a sequential target dosing mode to deliver treatment additive of predetermined composition to selected points along the piping at predetermined times and in predetermined concentrations.
U.S. Pat. No. 4,869,016 (Williams et al.) describes the synergistic effect of low dosage levels of chlorine ions used in conjunction with low dosage levels of copper ions to form a treatment additive sufficient to temporarily stress or disorient (but not “necessarily” kill) both macroorganisms and microorganisms so that they pass through the piping system of a facility without attaching themselves to the system. Being of low dosage, the chlorine and copper ions generated by this technique represent significantly less environmental concern than the previous techniques. As successful as this combined ion treatment approach may have been, it still suffered limitations as applied to large facilities. Combined ion treatment is effective for only a relatively short time duration (such as, for example, thirty (30) minutes). Thus, if combined ion treatment is used only at the water inlet to the piping system of a large facility, the treatment is effective for only part of the travel of the organisms through the piping system. Fouling can then occur in the downstream part of the piping system for which treatment effectiveness has been lost. Conversely, use of combined ion treatment at numerous points along the piping system requires a corresponding number of sources of ion generation, such as electrolytic cells for generating the treatment ions, with resultant increased capital costs and operating expenses, and can result in an environmentally unacceptable buildup of certain of the ions at discharge.
U.S. Pat. No. 6,599,432 (Kross) describes disinfecting compositions (such as chlorine dioxide) for dental unit water lines, particularly effective against microbial flora in biofilms which form on the luminal walls of the piping and reservoir components of dental equipment, as well as methods related to the use of such compositions to reduce microbial numbers in water-bearing dental and other equipment and maintain reduced levels on a continuous basis.
U.S. Pat. Nos. 7,000,280; 6,067,682; 5,924,158; 5,903,946; 5,384,929; 5,265,302; and the like describe pipeline pigs and pigging processes. All references cited in this text are incorporated herein by reference in their entirety.